Semiconductor structures comprising aluminum oxide

ABSTRACT

A semiconductor structure comprising aluminum oxide. The semiconductor structure comprises a dielectric material overlying a substrate. The aluminum oxide overlies the dielectric material in a first region of the structure. A second region of the structure includes a first titanium nitride portion overlying the dielectric material, magnesium over the first titanium nitride portion, and a second titanium nitride portion over the magnesium. Methods of forming the semiconductor structure including aluminum oxide are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/184,452, filed Feb. 19, 2014, pending, the disclosure of which ishereby incorporated herein in its entirety by this reference.

FIELD

Embodiments disclosed herein relate to semiconductor structuresincluding aluminum oxide and methods of forming such semiconductorstructures. More specifically, embodiments disclosed herein relate tothe semiconductor structures and to methods for forming semiconductorstructures comprising self-aligned aluminum oxide structures.

BACKGROUND

Fabrication of conventional semiconductor structures requires formingaligned features within the semiconductor structure. Frequently,photolithography or other lithographic techniques are used to form thealigned features within the semiconductor structure. However, as thenumber of patterning and photolithography acts increases, the processingtime and cost of fabricating the semiconductor structure, as well as thepotential for contamination and structural defects, increases.Accordingly, reducing the number of patterning steps is often a goal ofsemiconductor fabrication methods.

It may be desired to form aluminum oxide at select locations of asemiconductor structure. FIG. 1A illustrates a semiconductor structure100 at an intermediate processing stage. Aluminum oxide 116 may beformed over a substrate 110 including isolation regions 112. While thealuminum oxide 116 is only desired at a specific location (see FIG. 1C),the aluminum oxide 116 is initially formed over the entire substrate 110and portions subsequently removed. Additional semiconductor materials114 may be formed between the aluminum oxide 116 and the substrate 110.A bottom anti-reflective coating (BARC) 140 and a photoresist 150 may beformed over the aluminum oxide 116. Referring to FIG. 1B, portions ofthe photoresist 150 and the BARC 140 may be removed to produce a desiredpattern, which is transferred to the aluminum oxide 116. Referring toFIG. 1C, the aluminum oxide 116 may be removed through the patternedphotoresist 150 and BARC 140. However, removing the aluminum oxide 116may result in undesired damage to exposed materials of the semiconductorstructure 100. For example, etching aluminum oxide 116 often requiresaggressive etch chemistries that may damage materials of thesemiconductor structure 100, such as a dielectric material or a gateoxide. As an example, aluminum oxide may be removed by etching with asolution of ammonium hydroxide, hydrogen peroxide, and water. Theammonium hydroxide and hydrogen peroxide may have concentrations up toabout thirty weight percent (30 wt. %). Aluminum oxide may also beremoved with etchants such as Br₂ in a methanol solution, or withetchants including strong acids such as HF, HCl, phosphoric acid,sulfuric acid, and combinations thereof. The etch chemistries may alsoundercut the aluminum oxide 116 in regions where the aluminum oxide 116is desired. Because of the aggressive nature of such etchants, it may bedifficult to control the thickness of the aluminum oxide and to preventdamage to materials of the semiconductor structure 100, such asmaterials underlying the aluminum oxide. Thus, forming aluminum oxide indesired locations on a semiconductor structure is a challenge.

Therefore, it would be desirable to have a method of forming aself-aligned aluminum oxide material without damaging the materialsproximate to the aluminum oxide or undercutting the aluminum oxide. Itwould also be desirable to be able to form a self-aligned aluminum oxidematerial that does not require etching aluminum oxide and does notrequire a wet BARC and photoresist material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A through FIG. 1C are simplified cross-sectional views showingprocessing acts for forming an aluminum oxide material on desiredlocations of a substrate;

FIG. 2 is a simplified cross-sectional view showing a semiconductorstructure with an aluminum oxide material according to embodiments ofthe present disclosure;

FIG. 3A through FIG. 3F are simplified cross-sectional views showingprocessing acts for forming the semiconductor structure of FIG. 2according to some embodiments of the present disclosure;

FIG. 4A through FIG. 4C are simplified cross-sectional views showingprocessing acts for forming an aluminum oxide material on asemiconductor structure according to other embodiments of the presentdisclosure; and

FIG. 5A and FIG. 5B are simplified cross-sectional views showing analuminum oxide material on a semiconductor structure according to otherembodiments of the present disclosure.

DETAILED DESCRIPTION

The illustrations included herewith are not meant to be actual views ofany particular systems or memory structures, but are merely idealizedrepresentations that are employed to describe embodiments describedherein. Elements and features common between figures may retain the samenumerical designation except that, for ease of following thedescription, for the most part, reference numerals begin with the numberof the drawing on which the elements are introduced or most fullydiscussed.

The following description provides specific details, such as materialtypes, material thicknesses, and processing conditions, in order toprovide a thorough description of embodiments described herein. However,a person of ordinary skill in the art will understand that theembodiments disclosed herein may be practiced without employing thesespecific details. Indeed, the embodiments may be practiced inconjunction with conventional fabrication techniques employed in thesemiconductor industry. In addition, the description provided hereindoes not form a complete process flow for manufacturing semiconductorstructures, and the structures described below do not form a completesemiconductor device. Only those process acts and structures necessaryto understand the embodiments described herein are described in detailbelow. Additional acts to form a complete semiconductor device includingthe structures described herein may be performed by conventionaltechniques.

Methods of forming an aluminum-containing material on a semiconductorstructure are disclosed, as are semiconductor structures includingaluminum oxide. The aluminum-containing material may be formed by atomiclayer deposition (ALD), chemical vapor deposition (CVD), plasma enhancedchemical vapor deposition (PECVD), low pressure chemical vapordeposition (LPCVD), physical vapor deposition (PVD), or other filmdeposition processes. In some embodiments, the aluminum-containingmaterial is formed by ALD. Depending on the material over which thealuminum-containing material is initially formed, thealuminum-containing material may be aluminum oxide or a metal-aluminumcompound. In some embodiments disclosed herein, the aluminum-containingmaterial formed over a metal nitride material may form analuminum-containing metal compound including aluminum, the metal,oxygen, and nitrogen. As used herein, the term “metal-aluminum compound”refers to a compound including aluminum, the metal over which thealuminum-containing material is formed, oxygen, and nitrogen atoms. Themetal-aluminum compound is a reaction product of the aluminum, metal,oxygen, and nitrogen. The aluminum-containing material formed over othermaterials of the semiconductor structures may be aluminum oxide. Thus,the aluminum-containing material formed over the metal nitride may havea different composition than the aluminum-containing material formedover a different material, such as silicon, silicon dioxide, a high-kdielectric material, or other material. The metal-aluminum compound andthe aluminum oxide may exhibit a different etch selectivity to variousetchants, enabling the metal-aluminum compound to be selectively removedfrom the semiconductor structure. In some embodiments, themetal-aluminum compound is formed over a titanium nitride material.

Referring to FIG. 2, a semiconductor structure 200 is shown. Thesemiconductor structure 200 includes a substrate 210 that may includeisolation regions 212. Isolation regions 212 may be shallow trenchisolation regions formed of a dielectric material, such as silicondioxide. The substrate 210 may be a base material or construction uponwhich additional materials are formed. The substrate 210 may be asemiconductor substrate, a base semiconductor layer on a supportingstructure, a metal electrode or a semiconductor substrate having one ormore layers, structures or regions formed thereon. The substrate 210 maybe a conventional silicon substrate or other bulk substrate comprising alayer of semiconductive material. As used herein, the term “bulksubstrate” means and includes not only silicon wafers, but alsosilicon-on-insulator (“SOI”) substrates, such as silicon-on-sapphire(“SOS”) substrates and silicon-on-glass (“SOG”) substrates, epitaxiallayers of silicon on a base semiconductor foundation, and othersemiconductor or optoelectronic materials, such as silicon-germanium,germanium, gallium arsenide, gallium nitride, and indium phosphide. Thesubstrate may be doped or undoped.

The semiconductor structure 200 may include at least two regions, suchas region 205 and region 215. Although only one region 205 and oneregion 215 is shown in FIG. 2, the semiconductor structure 200 mayinclude several alternating portions of region 205 and region 215.Region 205 may, for example, include an n-type channel, such as an NMOStransistor having an n-channel, and region 215 may, for example, includea p-type channel, such as a PMOS transistor having a p-channel in acomplementary-metal-on-semiconductor (CMOS) structure. For convenience,region 205 is also referred to herein as the n-channel region 205 andregion 215 is also referred to herein as the p-channel region 215. Byway of example, n-channel region 205 may also include n-doped source anddrain regions 202, and p-channel region 215 may include p-doped sourceand drain regions 204. As explained in more detail below, only p-channelregion 215 may include aluminum oxide 224.

N-channel region 205 of the semiconductor structure 200 may include agate oxide 214 overlying the substrate 210. The gate oxide 214 mayinclude an oxide, such as a deposited or a thermally grown silicondioxide material. A high-k dielectric material 216 may overlie the gateoxide 214. Non-limiting examples of high-k dielectric material 216include, but are not limited to, hafnium oxide (such as, for example,HfO₂), titanium oxide (such as, for example, TiO₂), tantalum oxide (suchas, for example, Ta₂O₅), zirconium oxide (such as, for example, ZrO₂),niobium oxide (such as, for example, NbO, NbO₂, or Nb₂O₅), molybdenumoxide (such as, for example, MoO₂ or MoO₃), ruthenium oxide (RuO₂),strontium oxide (such as, for example, SrO), barium oxide (such as, forexample, BaO), strontium titanium oxide (SrTiO₃, also known as STO),magnesium oxide (such as, for example, MgO), or combinations thereof.

A gate stack 225 may overlie the high-k dielectric material 216. Thegate stack 225 may include a first metal material 218, a cappingmaterial 220, and a second metal material 222. The first metal material218 and the second metal material 222 may be formed of the same metal ordifferent metals. The first metal material 218 may be selected toprovide adhesion to the underlying high-k dielectric material 216. Insome embodiments, each of the first metal material 218 and the secondmetal material 222 is a metal nitride, such as titanium nitride.However, in other embodiments, the first metal material 218 may includecopper, tungsten, aluminum, titanium, tantalum, ruthenium, platinum,alloys thereof, nitrides thereof, heavily doped semiconductor material,a conductive silicide, or combinations thereof, and the second metalmaterial may include a metal nitride.

P-channel region 215 may include the gate oxide 214 overlying thesubstrate 210 and the high-k dielectric material 216 overlying the gateoxide 214. The gate oxide 214 and the dielectric material 216 inp-channel region 215 may be the same as those in n-channel region 205.Aluminum oxide 224 may overlie the high-k dielectric material 216. Thealuminum oxide 224 may increase the work function of the gate in region215. The aluminum oxide 224 may be located only in p-channel region 215of the semiconductor structure 200.

Accordingly, a semiconductor structure comprising an aluminum oxidematerial is disclosed. The semiconductor structure comprises adielectric material overlying a substrate. The structure includes afirst region comprising aluminum oxide overlying the dielectricmaterial. The semiconductor structure includes a second regioncomprising a first titanium nitride portion overlying the dielectricmaterial, magnesium over the first titanium nitride portion, and asecond titanium nitride portion overlying the magnesium.

A method of forming a semiconductor structure 300 including an aluminumoxide material is described with reference to FIG. 3A through FIG. 3F.Referring to FIG. 3A, isolation regions 312 may be formed in a substrate310 by conventional techniques, which are not described in detailherein. A gate oxide material 314 may be formed over the substrate 310.The gate oxide material 314 may be thermally grown or may be deposited,and may include a material such as silicon dioxide. While not shown,other materials may, optionally, intervene between the substrate 310 andthe gate oxide material 314 depending on the desired application of thesemiconductor structure 300. The substrate 310 may include source anddrain regions. For example, n-channel region 305 of the substrate 310may include n-doped source and drain regions 302 and p-channel region315 may include p-doped source and drain regions 304 located adjacentthe isolation regions 312. Source and drain regions 302 may be formed bydoping the semiconductor substrate 310 with n-type dopants, such asboron, as known in the art. Source and drain regions 304 may be formedby doping the semiconductor substrate 310 with p-type dopants, such asphosphorus, as known in the art.

A dielectric material 316 may be formed over the gate oxide material314. The dielectric material 316 may be a dielectric material such as asilicon oxide or a high-k dielectric material similar to high-kdielectric material described above with reference to high-k dielectricmaterial 216. In some embodiments, the dielectric material 316 ishafnium oxide. The dielectric material 316 may be formed by ALD, CVD,PECVD, LPCVD, PVD, or other film deposition processes.

Referring to FIG. 3B, a first metal material 318 may be formed over thedielectric material 316. The first metal material 318 may be selected toprovide adhesion to the dielectric material 316. In some embodiments,the first metal material 318 is a metal nitride, such as titaniumnitride. The first metal material 318 may have a thickness of betweenabout 10 angstroms (Å) and about 30 Å, such as between about 15 Å andabout 25 Å. In some embodiments, the first metal material 318 has athickness of about 20 Å.

A capping material 320 may overlie the first metal material 318. Thecapping material 320 may include a metal such as magnesium, magnesiumoxide, lanthanum, lanthanum oxide, or combinations thereof. In someembodiments, the capping material 320 is magnesium. The capping material320 may be selected to provide a decreased work function of the NMOSdevice in n-channel region 305. The capping material 320 may be formedto a thickness of between about 5 Å and about 15 Å, such as betweenabout 5 Å and about 10 Å. In some embodiments, the capping material 320has a thickness of about 8 Å. The capping material 320 may be formed byALD, CVD, PECVD, LPCVD, PVD, or other deposition processes.

A second metal material 322 may be formed over the capping material 320.The second metal material 322 may be formed of the same metal as thefirst metal material 318. In some embodiments, the second metal material322 is titanium nitride. In other embodiments, the second metal material322 may include a lower portion formed of a metal material or metalnitride and an exposed portion formed of a metal nitride. For example,in some embodiments, a lower portion of the second metal material 322 isa metal material and an exposed portion of the second metal material 322is titanium nitride.

The second metal material 322 may be formed to a greater thickness thanthe first metal material 318. The second metal material 322 may have athickness of between about 20 Å and about 60 Å, such as between about 30Å and about 50 Å, or between about 35 Å and about 45 Å. In someembodiments, the second metal material 322 has a thickness of about 40Å. The second metal material 322 may be formed by similar methods as thefirst metal material 318. For example, the second metal material 322 maybe formed by ALD, CVD, PECVD, LPCVD, PVD, or other suitable depositionprocess. As described in more detail below, the first metal material318, capping material 320, and second metal material 322 may form a gatestack 325 in the n-channel region 305.

A mask material 340 and a photoresist material 350 may be formed overthe semiconductor structure 300 and patterned to expose the second metalmaterial 322 in the p-channel region 315 of the semiconductor structure300. The mask material 340 may include a hardmask material or othersuitable masking material and may have a thickness of about 15 nm. Insome embodiments, the mask material 340 is a silicon nitride hardmask.The photoresist material 350 may be any conventional photoresistmaterial. The mask material 340 and photoresist material 350 may bepatterned by conventional techniques, which are not described in detailherein.

Referring to FIG. 3C, the second metal material 322, the cappingmaterial 320, and the first metal material 318 may be removed from thep-channel region 315 by reactive ion etching, such as with an oxygen ora nitrogen based plasma. The plasma may be, for example, a mixtureincluding nitrogen, boron trichloride, and argon (N₂/BCl₃/Ar), a mixtureincluding nitrogen, methane, and argon (N₂/CH₄/Ar), or a mixtureincluding oxygen, chlorine, and helium, (O₂/Cl₂/He). In otherembodiments, the second metal material 322, the capping material 320,and the first metal material 318 in the p-channel region 315 may beremoved with a solution including ammonium hydroxide (NH₄OH), hydrogenperoxide (H₂O₂), and water. The mask material 340 and photoresistmaterial 350 may protect the materials of the n-channel region 305 frombeing removed. The etchant may be nonreactive with the dielectricmaterial 316 and, therefore, the dielectric material 316 may function asan etch stop. The dielectric material 316 of p-channel region 315 may beexposed after removing the second metal material 322, the cappingmaterial 320, and the first metal material 318.

After the dielectric material 316 of p-channel region 315 is exposed,the photoresist material 350 and mask material 340 may be removed fromn-channel region 305 to expose the second metal material 322 ofn-channel region 305. Prior to removing the mask material 340, thedielectric material 316 may be crystallized to increase the etchselectivity of the mask material 340 relative to the dielectric material316. For example, the dielectric material 316 may be annealed tocrystallize the dielectric material 316. Thereafter, the mask material340 may be removed from n-channel region 305 without substantiallyremoving the dielectric material 316 exposed in p-channel region 315.After removing the mask material 340, the second metal material 322 maybe exposed in the n-channel region.

Referring to FIG. 3D, an aluminum-containing material 327 may be formedover exposed surfaces of the semiconductor structure 300. By way ofexample, the aluminum-containing material 327 may be conformally formedover the dielectric material 316 of p-channel region 315 and over thesecond metal material 322 of n-channel region 305. As explained in moredetail below, the aluminum-containing material 327 may be formed byconventional techniques, such as by an ALD process, a CVD process, aPECVD process, an LPCVD process, a PVD process, or other depositionprocess, using appropriately selected aluminum precursors and oxygenprecursors.

As a result of the conditions used to form the aluminum-containingmaterial 327, such as, for example, deposition temperature, thealuminum-containing material 327 may form as an aluminum oxide 324 onthe dielectric material 316 of p-channel region 315 and as ametal-aluminum compound 326 on the second metal material 322 ofn-channel region 305. Without being bound by any theory, it is believedthat the aluminum of the aluminum-containing material 327 foamed on thesecond metal material 322 may react with the metal of the second metalmaterial 322, forming the metal-aluminum compound 326. In someembodiments, the metal-aluminum compound 326 may also form on thesidewalls of the gate stack 325 where the first metal material 318 andthe second metal material 322 are exposed. The metal-aluminum compound326 may be a reaction product of aluminum from the aluminum-containingmaterial 327, the metal from the second metal material 322, oxygen fromthe aluminum-containing material 327, and nitrogen from the second metalmaterial 322. In some embodiments, the second metal material 322 istitanium nitride. Thus, the metal-aluminum compound 326 may includealuminum, titanium, nitrogen, and oxygen atoms. In some embodiments, thealuminum compound 326 is a material such as AlTiO_(x)N_(y), where x isbetween one (1) and four (4) and y is between one-half (½) and two (2).In other embodiments, x is about 2.5 and y is about 0.8. Themetal-aluminum compound 326 may include about nineteen atomic percent(19 at. %) of each of aluminum and titanium, about forty-seven atomicpercent (47 at. %) of oxygen, and about fifteen atomic percent (15 at.%) of nitrogen.

Thus, exposing the semiconductor substrate 300 to the aluminum precursorand the oxygen precursor may form different aluminum-containingmaterials on n-channel region 305 and p-channel region 315 of thesemiconductor structure 300. Aluminum oxide 324 may be formed onp-channel region 315 and the metal-aluminum compound 326 may be formedon n-channel region 305 of the semiconductor structure 300.

The aluminum oxide 324 and the metal-aluminum compound 326 may be formedby exposing the semiconductor structure 300 to the aluminum precursorand the oxygen precursor. The aluminum oxide 324 and the metal-aluminumcompound 326 may be formed by a deposition process including an aluminumprecursor and an oxygen precursor. The aluminum precursor may includetris(diethylamino) aluminum (TDEAA), alkyl aluminum precursors such astri-methyl aluminum (TMA), aluminum alkoxides such as aluminumisopropoxide (AIP), aluminum tri-sec-butoxide (ATSB), aluminum ethoxide,dimethylaluminumhydride (DMAH), aluminumtris(2,2,6,6-tetramethyl-3,5-heptanedionate), triisobutylaluminum(TIBA), tris(dimethylamido)aluminum(III), or combinations thereof. Theoxygen precursor may include oxygen (O₂), ozone (O₃), water, orcombinations thereof. In some embodiments, the aluminum precursor is TMAand the oxygen containing precursor is water.

In some embodiments, the aluminum-containing material may be formed byALD. The aluminum-containing material 327 may be formed by performingbetween one ALD cycle and ten ALD cycles. For example, between one ALDcycle and five ALD cycles or between five ALD cycles and ten ALD cyclesmay be performed. The aluminum oxide 324 may be formed to a thickness ofbetween about 5 Å and about 10 Å, such as between about 5 Å and about 8Å. The metal-aluminum compound 326 may be formed to a greater thicknessthan the aluminum oxide 324. Without being bound by any theory, it isbelieved that the thickness of the metal-aluminum compound 326 may begreater than the thickness of the aluminum oxide 324 because of theincorporation of the second metal material 322 and nitrogen in themetal-aluminum compound 326.

The deposition process may be performed at a temperature from betweenabout 200° C. and about 400° C., such as between about 250° C. and about350° C. In some embodiments, the deposition is performed at atemperature of about 300° C., which enhances the formation of themetal-aluminum compound 326 over the second metal material 322.

With continued reference to FIG. 3D, the aluminum oxide 324 may beformed only in p-channel region 315 and the metal-aluminum compound 326may be formed only in n-channel region 305 of the semiconductorstructure 300. Thus, the aluminum oxide 324 may be selectively formedover only the dielectric material 316 of p-channel region 315. Althoughthe metal-aluminum compound 326 and the aluminum oxide 324 are formedconcurrently, the composition of the metal-aluminum compound 326 may bedifferent than the composition of the aluminum oxide 324. Since thealuminum oxide 324 only forms over the dielectric material 316 and themetal-aluminum compound 326 only forms over the second metal material322, the formation of the different aluminum-containing materials may beself-aligned on the respective regions of the semiconductor structure300.

Referring to FIG. 3E, after the aluminum oxide 324 and themetal-aluminum compound 326 are formed, the metal-aluminum compound 326may be selectively removed from the semiconductor structure 300 suchthat only the aluminum oxide 324 of the aluminum-containing material 327(FIG. 3D) remains in p-channel region 315 of the semiconductor structure300.

The aluminum oxide 324 and the metal-aluminum compound 326 may exhibitdifferent etch rates when exposed to various etchants. For example, themetal-aluminum compound 326 may be removed using an aqueous solution ofH₂O₂, whereas the aluminum oxide 324 may exhibit a low removal rate uponexposure to the aqueous H₂O₂ solution. By way of example only, themetal-aluminum compound 326 may have an etch rate that is at least about10 times greater than that of the aluminum oxide 324 when exposed to theH₂O₂ solution. Thus, the metal-aluminum compound 326 may be removed byexposing the semiconductor structure 300 to H₂O₂. However, exposing thealuminum oxide 324 to the H₂O₂ solution may not remove any or may removeonly a small portion of the aluminum oxide 324. Because the aluminumoxide 324 is not removed by exposure to the H₂O₂ solution, the aluminumoxide 324 may also protect underlying materials from being damaged bythe H₂O₂ solution. The H₂O₂ solution may also clean the surface of thesemiconductor structure 300 prior to forming additional materialsthereover.

The metal-aluminum compound 326 may be removed at a rate ofapproximately 50 Å per minute when exposed to the H₂O₂ solution. Thus,an metal-aluminum compound 326 having a thickness of between about 10 Åand about 20 Å may be removed by exposing the metal-aluminum compound326 to the H₂O₂ solution for less than approximately one minute, such asless than about thirty seconds. In some embodiments, the semiconductorstructure 300 is exposed to a solution of H₂O₂ for a period of timeranging from between about ten seconds to about three minutes, such asbetween about thirty seconds and about one minute, or between about oneminute and about two minutes. In some embodiments, the semiconductorstructure 300 is exposed to an H₂O₂ solution for about one minute tosubstantially remove the metal-aluminum compound 326 while the aluminumoxide 324 remains in p-channel region 315.

The H₂O₂ solution may be formed of H₂O₂ and water. The H₂O₂ solution mayhave a H₂O₂ concentration ranging from between about one weight percent(1 wt. %) to about ten weight percent (10 wt. %), such as between aboutthree weight percent (3 wt. %) and about seven weight percent (7 wt. %).In some embodiments, the H₂O₂ solution includes between about threeweight percent (3 wt. %) and about five weight percent (5 wt. %) H₂O₂.

The semiconductor structure 300 may be exposed to the H₂O₂ solution at atemperature of between about 20° C. and about 100° C., such as betweenabout 25° C. and about 75° C. In some embodiments, the H₂O₂ solution isapplied at a temperature of about room temperature (e.g., between about20° C. and about 25° C.). In other embodiments, the H₂O₂ solution isapplied at a temperature of about 65° C.

Referring to FIG. 3E, the aluminum oxide 324 remains on p-channel region315 of the semiconductor structure 300 while no aluminum-containingmaterial 327 is present on the n-channel region 305. Thus, the aluminumoxide 324 may be formed at a desired location on the semiconductorstructure 300 and may be self-aligned without using an additionalphotolithography act to pattern the aluminum oxide 324. By eliminatingthe need for the additional photolithography act, the complexity andcost of the method of the present disclosure may be reduced compared toconventional techniques of forming and patterning aluminum oxide 324. Inaddition, the use of extra materials, such as a photoresist and BARC, isavoided. The methods of embodiments of the present disclosure may alsoenable reduction in the number of etch acts and etchants used. Since nophotoresist and BARC are used, only a single etchant, aqueous H₂O₂, isneeded, which further reduces the complexity and cost of the methods ofembodiments of the present disclosure.

Referring to FIG. 3F, a conductive material 328 may be conformallyformed over the semiconductor structure 300. The conductive material 328may be formed over the second metal material 322 in n-channel region 305and over the aluminum oxide 324 in p-channel region 315. The conductivematerial 328 may be formed by ALD, CVD, PECVD, LPCVD, PVD, or otherdeposition method. The conductive material 328 may have a thickness ofbetween about 40 Å and about 60 Å, such as between about 45 Å and about55 Å. In some embodiments, the thickness of the conductive material 328is about 50 Å. The conductive material 328 may include a metal or ametal nitride. The conductive material 328 may include the same metal asthe first metal material 318 or the second metal material 322. Thus, insome embodiments, the conductive material 328, the first metal material318, and the second metal material 322 are the same material. In someembodiments, the conductive material 328 is titanium nitride.

With continued reference to FIG. 3F, a silicon material 330 may beformed over the conductive material 328. The silicon material 330 may beformed by suitable methods, such as PVD, ALD, CVD, PECVD, LPCVD, PVD, orother deposition methods. The silicon material 330 may have a thicknessof between about 2 nm and about 10 nm, such as between about 3 nm andabout 8 nm, and between about 4 nm and about 6 nm. In some embodiments,the silicon material 330 has a thickness of about 5 nm.

After the silicon material 330 is formed, a mask may be formed overp-channel region 315. N-channel region 305 may be implanted with arsenicto form arsenic implanted regions (not shown) at an interface betweenthe first metal material 318 and the capping material 320 and at aninterface between the capping material 320 and the second metal material322. After the arsenic implant is complete, the mask material may beremoved from the semiconductor structure 300.

A polysilicon material 332 may be formed over the silicon material 330.The polysilicon material 332 may be doped with boron or doped withphosphorus. In some embodiments, the polysilicon material 332 is dopedwith phosphorus. The polysilicon material 332 may be formed by formingpolysilicon and then doping with phosphorus, or the polysilicon material332 may be formed in situ. In some embodiments, the polysilicon material332 is formed in situ by including dopant gases such as phosphine ordiborane in the deposition precursor gas recipe.

A second conductive material 334 may be formed over the polysiliconmaterial 332. The second conductive material 334 may include aconductive metal such as copper, tungsten, aluminum, titanium, tantalum,platinum, alloys thereof, heavily doped semiconductor material, aconductive silicide, or combinations thereof. In some embodiments, thesecond conductive material 334 is tungsten.

A silicon nitride material 336 may overlie the second conductivematerial 334. The silicon nitride material 336 may be formed by asuitable deposition process, such as ALD, CVD, PECVD, LPCVD, PVD, orother deposition process.

Additional processing acts may be performed by conventional techniquesto produce a complete semiconductor device, such as a CMOS device orDRAM memory cell, according to the desired end use of the semiconductorstructure 300.

Accordingly, a method of forming a semiconductor structure is disclosed.The method comprises exposing a dielectric material and a metal nitrideon a substrate to an aluminum precursor and an oxygen precursor to formaluminum oxide over the dielectric material and a metal-aluminumcompound over the metal nitride. The aluminum oxide and themetal-aluminum compound are exposed to a solution comprising hydrogenperoxide.

A method of forming a semiconductor structure 400 having an aluminumoxide material with a thickness less than about 20 Å, such as less thanabout 10 Å, is described with respect to FIG. 4A through FIG. 4C.Referring to FIG. 4A, titanium nitride 420 may be formed over asubstrate 410. Although not shown, there may be intervening materialsbetween the titanium nitride 420 and the substrate 410, such as at leastone of a dielectric material, conductive material, work functionmodifier, or other materials. For example, a conductive material such ascopper, tungsten, aluminum, titanium, tantalum, platinum, alloysthereof, heavily doped semiconductor material, a conductive silicide, orcombinations thereof may underlie the titanium nitride 420. The titaniumnitride 420 may be patterned with a photomask or a hardmask material byconventional techniques, which are not described in detail herein.Desired portions of the titanium nitride 420 may be removed throughopenings in the mask. For example, the titanium nitride 420 may beexposed to an aqueous solution of H₂O₂ or a solution of ammoniumhydroxide. In some embodiments, the titanium nitride 420 is removed withan H₂O₂ solution at a rate of about 10 Å per minute.

Referring to FIG. 4B, an aluminum-containing material 427 may beconformally formed on the semiconductor structure 400. The substrate 410(or intervening materials, if present) and the titanium nitride 420 maybe exposed to the aluminum precursor and the oxygen precursor at atemperature of between about 200° C. and about 400° C., such as betweenabout 250° C. and about 300° C., or between about 300° C. and about 350°C. The aluminum-containing material 427 includes a metal-aluminumcompound 440 and aluminum oxide 430. In some embodiments, thetemperature is about 300° C. Exposing the substrate 410 to the aluminumprecursor and the oxygen precursor may form the aluminum oxide 430 overthe substrate 410 and the metal-aluminum compound 440 over the titaniumnitride 420. As previously described, the metal-aluminum compound 440may be AlTiN_(y)O_(x), where x is between one (1) and four (4) and y isbetween one-half (½) and two (2). In other embodiments, x is about 2.5and y is about 0.8. The metal-aluminum compound 440 may comprise aboutnineteen atomic percent (19 at. %) of each of aluminum and titanium,about forty-seven atomic percent (47 at. %) of oxygen, and about fifteenatomic percent (15 at. %) of nitrogen.

In some embodiments, the aluminum-containing material 427 is formed byALD. The aluminum-containing material 427 may be formed by performingbetween one ALD cycle and ten ALD cycles. For example, between one ALDcycle and five ALD cycles or between five ALD cycles and ten ALD cyclesmay be performed. The aluminum oxide 430 may have a thickness of betweenabout 5 Å and about 15 Å, such as between about 5 Å and about 10 Å, orbetween about 10 Å and about 15 Å. The metal-aluminum compound 440 mayhave a thickness that is greater than the thickness of the aluminumoxide 430.

Referring to FIG. 4C, the metal-aluminum compound 440 may be removed byexposing the semiconductor structure 400 to a solution of H₂O₂, asdescribed above with reference to FIG. 3E. For example, themetal-aluminum compound 440 may be removed by exposing the semiconductorstructure 400 to a solution of between about three weight percent (3 wt.%) and about ten weight percent (10 wt. %) H₂O₂ for between about tenseconds and about three minutes. The aluminum oxide 430 may remain onthe substrate 410. In some embodiments, additional processing acts maybe performed to remove the titanium nitride 420 from the semiconductorstructure 400. For example, the titanium nitride 420 may be removed at arate of about 10 Å per minute by exposing the titanium nitride 420 tothe H₂O₂ solution.

Thus, the resulting semiconductor structure 400 may include aluminumoxide 430 on desired portions of the substrate 410. In embodimentsincluding intervening materials between the substrate 410 and thetitanium nitride 420, the resulting semiconductor structure 400 mayinclude the intervening materials.

Accordingly, a method of forming aluminum oxide is disclosed. The methodcomprises forming titanium nitride on portions of a substrate. Atitanium-aluminum compound is formed over the titanium nitride andaluminum oxide is formed over the substrate. The titanium-aluminumcompound and the aluminum oxide are exposed to hydrogen peroxide toremove the titanium-aluminum compound from over the titanium nitride.

Referring to FIG. 5A, a method of forming an aluminum oxide comprising athickness greater than about 10 Å, such as greater than about 20 Å, isdescribed. Titanium nitride 520 may be patterned as described above withreference to FIG. 4A. The titanium nitride 520 and a substrate 510 maybe exposed to precursors for forming aluminum oxide, such as an aluminumprecursor and an oxygen precursor, to form aluminum oxide 530 over thesubstrate 510 and over the titanium nitride 520. The aluminum oxide 530may be formed to a thickness greater than about 10 Å, such as up toabout 30 Å, up to about 50 Å, or up to about 100 Å. Forming greater thanabout 20 Å of aluminum oxide 530 over a semiconductor structure 500 mayform an aluminum oxide 530 over the titanium nitride 520 rather than anmetal-aluminum compound 440 as described above with reference to FIG.4B. Aluminum oxide 530 may not be formed over on the sidewalls of thetitanium nitride 520.

Referring to FIG. 5B, the titanium nitride 520 may be removed byexposing the semiconductor structure 500 to an H₂O₂ solution. The H₂O₂solution may remove exposed portions of the titanium nitride 520, suchas side portions extending above the aluminum oxide 530 in between thetitanium nitride 520. Accordingly, a self-patterned aluminum oxide 530having a thickness greater than approximately 10 Å may be formed. Thealuminum oxide 530 between the titanium nitride 520 may have a thicknessthat is less than a thickness of the titanium nitride 520.

Accordingly, a method of forming an aluminum oxide material isdisclosed. The method comprises subjecting exposed portions of asubstrate and titanium nitride to an aluminum precursor and an oxygenprecursor to form aluminum oxide on the exposed portions of thesubstrate and a titanium-aluminum compound on the exposed portions ofthe titanium nitride. The titanium-aluminum compound is removed from thetitanium nitride.

In some embodiments, a self-aligned lanthanum oxide (La₂O₃) or magnesiumoxide (MgO) may be formed by methods similar to the above disclosedmethods of forming aluminum oxide. For example, a semiconductorstructure may comprise exposed portions of a metal nitride and exposedportions comprising another material. The semiconductor structure may beexposed to a lanthanum precursor and an oxygen precursor to form ametal-lanthanum compound over the metal nitride and lanthanum oxide overthe other exposed portions of the semiconductor structure. Themetal-lanthanum compound and the lanthanum oxide may be formed by ALD,CVD, PECVD, LPCVD, PVD, or other deposition process. Where the metalnitride comprises titanium nitride, the metal-lanthanum compound maycomprise lanthanum, titanium, nitrogen, and oxygen atoms, and mayexhibit a different etch rate than the lanthanum oxide upon exposure tovarious etchants. Similarly, a metal-magnesium compound may be formedover a metal nitride and a magnesium oxide may be formed over otherexposed portions of a semiconductor structure by exposing thesemiconductor structure to a magnesium precursor and an oxygenprecursor. The magnesium oxide may be formed by ALD, CVD, PECVD, LPCVD,PVD, or other deposition process. Where the metal nitride of thesemiconductor structure comprises titanium nitride, a titanium-magnesiumcompound comprising magnesium, titanium, nitrogen, and oxygen may beformed over the titanium nitride and magnesium oxide may be formed overother exposed portions of the semiconductor structure.

While certain illustrative embodiments have been described in connectionwith the figures, those of ordinary skill in the art will recognize andappreciate that embodiments encompassed by the disclosure are notlimited to those embodiments explicitly shown and described herein.Rather, many additions, deletions, and modifications to the embodimentsdescribed herein may be made without departing from the scope ofembodiments encompassed by the disclosure, such as those hereinafterclaimed, including legal equivalents. In addition, features from onedisclosed embodiment may be combined with features of another disclosedembodiment while still being encompassed within the scope of thedisclosure as contemplated by the inventors.

1. A semiconductor device comprising an aluminum oxide material,comprising: a dielectric material overlying a substrate; a first regionof the substrate, comprising: aluminum oxide overlying the dielectricmaterial; and a second region of the substrate, comprising; a firsttitanium nitride portion overlying the dielectric material; magnesiumover the first titanium nitride portion; and a second titanium nitrideportion overlying the magnesium.
 2. The semiconductor device of claim 1,wherein the dielectric material overlying the substrate compriseshafnium oxide.
 3. The semiconductor device of claim 1, wherein a bottomsurface of the first titanium nitride portion of the second region ofthe substrate is coplanar with a bottom surface of the aluminum oxide ofthe first region of the substrate.
 4. The semiconductor device of claim1, wherein the aluminum oxide has a thickness of between about 5 Å andabout 10 Å.
 5. The semiconductor device of claim 1, further comprising aconductive material overlying the aluminum oxide and the second titaniumnitride portion.
 6. The semiconductor device of claim 1, wherein thesecond titanium nitride portion has a thickness of between about 20 Åand about 60 Å.
 7. The semiconductor device of claim 1, furthercomprising a metal-aluminum compound over the second titanium nitrideportion.
 8. The semiconductor device of claim 7, wherein themetal-aluminum compound comprises aluminum, titanium, oxygen, andnitrogen.
 9. The semiconductor device of claim 1, wherein the firstregion of the substrate comprises a p-type channel.
 10. A semiconductordevice comprising: titanium nitride overlying a first portion of a gateoxide material; aluminum oxide overlying a second portion of the gateoxide material; a conductive material overlying and in contact with eachof the titanium nitride and the aluminum oxide.
 11. The semiconductordevice of claim 10, further comprising: a capping material over thetitanium nitride; and a metal nitride over the capping material.
 12. Thesemiconductor device of claim 10, further comprising a capping materialcomprising magnesium, magnesium oxide, lanthanum, lanthanum oxide, orcombinations thereof over the titanium nitride.
 13. The semiconductordevice of claim 10, wherein at least a portion of the titanium nitrideis coplanar with at least a portion of the aluminum oxide.
 14. Thesemiconductor device of claim 10, further comprising a polysiliconmaterial over the conductive material.
 15. The semiconductor device ofclaim 14, further comprising another conductive material over thepolysilicon material.
 16. The semiconductor device of claim 10, whereinthe titanium nitride has a thickness between about 30 Å and about 50 Å.17. The semiconductor device of claim 10, wherein the aluminum oxide hasa thickness between about 5 Å and about 10 Å.
 18. A semiconductordevice, comprising: aluminum oxide over at least a portion of asubstrate; and titanium nitride over at least another portion of thesubstrate, at least one surface of the titanium nitride coplanar with atleast one surface of the aluminum oxide.
 19. The semiconductor device ofclaim 18, further comprising a gap between the aluminum oxide and thetitanium nitride.
 20. The semiconductor device of claim 18, wherein thealuminum oxide has a thickness of between about 5 Å and about 15 Å.